1. Preheat oven to 375°F (190°C) and line a 12-cup muffin tin with paper liners, greasing the tops of the cups.

2. In a large bowl, whisk together flour, baking powder, baking soda, and salt until well combined.

3. In another bowl, whisk sugar and eggs, then add melted butter, sourdough discard, milk, orange juice, vanilla extract, and orange zest until smooth.

4. Pour wet ingredients into dry ingredients and gently fold with a spatula until just combined, being careful not to overmix.

5. Fold in cranberries, adding them frozen if using to prevent bleeding.

6. Divide batter evenly among muffin cups, filling each about three-quarters full, and sprinkle tops with coarse sugar if desired.

7. Bake for 18–22 minutes until tops are golden and a toothpick inserted in the center comes out clean, rotating pan halfway if needed.

8. Allow muffins to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.